1. Field of the Invention
The present invention relates to an improvement in the process wherein a solid polymer slurry diluted with a specific diluent is continuously discharged from a high pressure zone (hereinafter called the "first zone") to a low pressure zone substantially maintained at atmospheric pressure (hereinafter called the "the second zone") and, in this discharge, the slurry is separated into said diluent and a dried polymer, the improvement wherein the discharge amount of the solid polymer slurry is strictly controlled.
2. Description of the Prior Art
Some proposals have already been made in various U.S. Patents, such as U.S. Pat. Nos. 3,285,899, 3,428,619, and 4,126,743 as to processes for continuously extracting a slurry of a solid polymer dispersed in a liquid diluent containing at least one kind of hydrocarbon(s) which are gaseous at normal temperature and under normal pressure and, at the same time, separating the diluting agent and the solid polymer.
Particularly, a proposal has been made in said U.S. Pat. No. 4,126,743 as to a process for controlling the discharge amount without relying upon any mechanical means, but enabling one to exert a wide range of control. Namely, what has been proposed is a process for controlling the discharge amount of the slurry by adjusting the quantity of heat transmitted to a heat piping into which the slurry is discharged by controlling the amount of steam introduced into heating jackets surrounding the heating pipe. Such process permits a wide range of control over said discharge and is not at all a mechanical process for controlling the discharge amount; hence it is an excellent process suitable for use on an industrial basis.
With respect to the process of U.S. Pat. No. 4,126,743, however, there are various difficulties in actually adjusting the quantity of heat involved in the steam used for heating. In other words, a large amount of steam has to be introduced and discharged in order to control the amount of heat when the control depends on the amount of steam introduced into a single heating jacket as described in FIG. 1 of said U.S. Pat. No. 4,126,743. This means that the process is not one that effectively utilizes the steam as a heat source and so it is necessary to modify the process to make it workable on an industrial scale by attaching to the system various devices to reuse or recycle the discharged steam.
In FIG. 3 of said U.S. Pat. No. 4,126,743, another embodiment of the process is shown, which embodiment is to divide the jacket for heating into two or more and effect the control by the number of the heating jackets into which the steam is to be introduced. This embodiment makes more efficient use of the steam, but involves a problem in that the variation of the discharge amount of slurry oecomes discontinuous and so strict control of the discharge amount of the slurry becomes impossible.